安宁河断裂紫马跨一带晚第四纪地貌变形与断层位移速率  

LATE QUATERNARY GEOMORPHIC DEFORMATION AND DISPLACEMENT RATES OF THE ANNINGHE FAULT AROUND ZIMAKUA

作　　者：冉勇康[1] 程建武[1] 宫会玲[1] 陈立春[1] 

机构地区：[1]中国地震局地质研究所,北京100029

出　　处：《地震地质》2008年第1期86-98,共13页Seismology and Geology

基　　金：国家重点基础研究发展计划项目(2004CB418401)资助

摘　　要：紫马跨一带是安宁河断裂北段晚第四纪断错地层地貌序列保存最好的地区,通过数字影像分析、全站仪实测和探槽开挖,对该地点断错现象进行细致研究,获得了晚全新世以来的左旋位移速率为6.2mm/a,垂直位移速率1.4mm/a;距今约10ka以来的平均左旋位移速率3.6-4.0mm/a,垂直位移速率约为1.1mm/a;距今约20ka以来的左旋位移速率为3.8-4.2mm/a,垂直位移速率最小为0.9mm/a。断层水平和垂直位移速率的比例约为4∶1。断层位移速率在时间分布上的变化与古地震研究的丛集复发特征有较好的一致性,反映断裂的活动强度存在强弱活动的交替现象。The Anninghe Fault is an important active fauh along the eastern boundary of Sichuan-Yunnan active tectonic block,and the study of its distribution feature of displacement rates in the late Quaternary is of fundamental importance for understanding the dynamic theory on Chinese continent, boundary dynam Anninghe ic process of the active block and the recurrence interval of large earthquakes. The active Fault in late Quaternary has the length of 160km and consists of two segments. Zimakua is an area where the latest neotectonic rupture trajectories are relatively simple and the offset geomorphologic sequences are well developed. Using the methods of detailed geomorphic and geological survey, digital image analysis, total station instrument survey, excavation of trench and dating, the paper makes an analysis on the geomorphologic sequences of the strata and obtains some new results as follows： The terrace（step） T3 consisting of moraine deposits was formed at about 20ka BP and offset by the Anninghe Fault with a left-lateral displacement of （84 ± 3 ）m and a vertical displacement of 18m. On the base of the moraine deposits overlies terrace（step） T2 of mainly alluvial deposits formed at 10 -7ka BP with the maximum left-lateral displacement of about 40m, an average of （36 ± 4） m, and a vertical displacement of about 1 lm. Terrace T, is composed mainly of the alluvium and partial dammed-pond deposits which were formed during 3 -2.2ka BP. The earliest event that offset the T, happened at 1.7ka BP. Three events have been discovered since 1.7ka BP and the cumulative left-lateral displacement is 10.5m and the vertical displacement 2.3m. So, the left-lateral displacement rates are 6.2mm/a,3.6 - 4mm/a,3.8 - 4.2mm/a and the vertical rates are 1.4mm/a, 1. 1mm/a,0.9mm/a（ at least） on average in about 2.6ka, 10ka and 20ka,respectively. The proportion of horizontal to vertical displacements is about 4 ： 1. That means the vertical rate on Anninghe Fault is about 25% of horizontal slip rate. The left-lateral

关 键 词：安宁河断裂 晚第四纪 地层地貌序列 位移速率 

分 类 号：P315.2[天文地球—地震学]